JP2017002937A - Bearing and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous bearing which inhibits pores from being crushed during manufacturing, and to provide a manufacturing method for the porous bearing.SOLUTION: A manufacturing method for a porous bush, which is formed by a sintered compact and has recessed parts on a bearing surface which receives a pin, includes: a molding step where metal powder KF is compressed into a predetermined shape to mold a green compact 50; and a sintering step where the green compact 50 molded in the molding step is sintered. The recessed parts are formed in the molding step.SELECTED DRAWING: Figure 12

Description

  The present invention relates to a porous bearing made of a sintered body and a method for manufacturing the same.

  Conventionally, as a manufacturing method of this type of bearing, for example, the one disclosed in Patent Document 1 is known. In such a bearing manufacturing method, sizing (pressing with a mold for the purpose of improving dimensional accuracy) is performed on a cylindrical sintered metal material obtained by compression molding metal powder and firing it. Then, a dynamic pressure groove (concave portion) is formed on the bearing surface by a bearing surface molding process.

  The molding equipment used in the bearing surface molding process is a cylindrical die that press-fits the outer peripheral surface of the sintered metal material, a core rod that molds the inner peripheral surface of the sintered metal material, and both end surfaces of the sintered metal material in the vertical direction. The upper and lower punches that hold down from the main elements. An uneven mold corresponding to the shape of the bearing surface of the finished product (bearing) is provided on the outer peripheral surface of the core rod. The convex portion of the molding die forms a dynamic pressure groove on the bearing surface.

  Then, after placing the sintered metal material in alignment with the upper surface of the die, the upper punch and core rod are lowered to press the sintered metal material into the die, and the sintered metal material is pressed against the lower punch and sintered. Pressurize the metal material from above and below. Then, the sintered metal material is deformed by receiving pressure from the die and the upper and lower punches, and the inner peripheral surface is pressed by the core rod forming die. As a result, the shape of the mold is transferred to the inner peripheral surface of the sintered metal material, and the dynamic pressure grooves are formed on the bearing surface (the inner peripheral surface of the sintered metal material) of the bearing (finished product).

JP 2002-178089 A

  By the way, in the bearing manufacturing method as described above, in the bearing surface forming process, the inner peripheral surface of the sintered sintered porous metal material is pressed against an uneven mold provided on the outer peripheral surface of the core rod. By deforming, dynamic pressure grooves are formed on the bearing surface of the bearing (the inner peripheral surface of the sintered metal material). For this reason, there exists a problem that the pore of the part in which the dynamic pressure groove in the bearing was formed will be crushed.

  The present invention has been made paying attention to such problems existing in the prior art. An object of the present invention is to provide a porous bearing capable of preventing the pores from being crushed during production and a method for producing the same.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
A bearing manufacturing method that solves the above problems is a method for manufacturing a porous bearing that is formed of a sintered body and has a recess on a bearing surface that receives a shaft, and compresses metal powder to form a green compact. And a sintering step of sintering the green compact molded in the molding step, and the recess is formed in the molding step.

  According to this configuration, since the recess is formed in the molding step of molding the green compact before the sintering step of sintering the green compact, the pores of the porous bearing that is the finished product are formed. It can suppress crushing at the time of manufacture.

  In the bearing manufacturing method, the bearing surface and the recess are preferably formed by compressing the metal powder in a state where a core rod is disposed in the metal powder in the forming step.

According to this structure, a bearing surface and a recessed part can be formed at once.
In the bearing manufacturing method, the core rod includes a hollow case having a through-hole in a peripheral surface, a protruding / retracting member inserted through the through-hole so as to be freely protruded / recessed, and inserted into the case to engage with the protruding / retracting member And an engaging pin that causes the protruding member to protrude from the through hole, and the protruding member protrudes from the through hole by engaging with the engaging pin in the molding step, and the core rod is It is preferable that after the green compact is molded, the engagement state between the projecting member and the engagement pin is released, and then the green compact is pulled out from the green compact along the axial direction of the core rod.

  According to this configuration, by releasing the engaged state between the retracting member and the engaging pin, the retracting member is allowed to enter the through hole, so that the core rod can be pulled out of the green compact.

  In the above bearing manufacturing method, the projecting member has an inclined surface whose height in the projecting direction decreases toward the pulling direction at the end on the pulling direction side of the core rod from the green compact. Is preferred.

  According to this configuration, when the core rod is pulled out of the green compact, the protruding and retracting member receives a reaction force from the inclined surface of the green compact corresponding to the inclined surface on the inclined surface, so that the protruding and retracting member enters the through hole. Pressed. For this reason, since the resistance by the protruding and retracting member when the core rod is pulled out from the green compact is reduced, the core rod can be easily pulled out from the green compact.

  A bearing that solves the above problems is a porous bearing that is formed of a sintered body and has a recess on a bearing surface that receives a shaft, and at least a molding step of compressing metal powder to form a green compact; And the sintering step of sintering the green compact molded in the molding step, and the recess is formed in the molding step.

  According to this configuration, since the recess is formed in the molding step of molding the green compact before the sintering step of sintering the green compact, the pores of the porous bearing that is the finished product are formed. It can suppress crushing at the time of manufacture.

  A bearing that solves the above problems is a porous bearing that is formed of a sintered body and has a recess on a bearing surface that receives a shaft, and the recess is formed in a molding step by compressing metal powder to form a green compact. As a result, the pores of the bearing surface where the recess is formed and the pores where the recess is not formed are in the same state.

  According to this configuration, since the recess is formed in the molding step of molding the green compact before the sintering step of sintering the green compact, the pores of the porous bearing that is the finished product are formed. It can suppress crushing at the time of manufacture. For this reason, the pores of the bearing surface where the recesses are formed and the pores where the recesses are not formed are in the same state. Therefore, when lubricating oil is included in the bearing, the bearing surface Lubricating oil can be permeated smoothly and stably from the pores.

  According to the present invention, it is possible to prevent the pores from being crushed during production.

The disassembled perspective view which shows a part of chain in one Embodiment. Sectional drawing of the chain. Sectional drawing of the bush of the chain. The front schematic diagram of a metal mold apparatus. The front view which shows a state when the protrusion / projection member protrudes from the through-hole of a case in a core rod. FIG. 6 is a cross-sectional view taken along line 6-6 in FIG. The perspective view which shows the state inside the case of the core rod of FIG. The front view which shows a state when the intruding member does not protrude from the through-hole of a case in a core rod. FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 8. The perspective view which shows the state inside the case of the core rod of FIG. The schematic diagram which shows operation | movement of the engagement pin in the case of a core rod. (A)-(j) is a cross-sectional schematic diagram which shows a formation process. (A)-(c) is a principal part expansion schematic diagram which shows the operation | movement when pulling out a core rod.

Hereinafter, an embodiment in which a bearing is embodied as a bush of a chain will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the chain 11 of the present embodiment includes an inner link 13 configured to include two inner link plates 12 that face each other in the width direction Y, and two outer link plates that also face each other. 14 and an outer link 15 including 14.

  The inner link 13 is a link in which the distance between the two opposing inner link plates 12 is relatively narrower than that of the outer link 15, and the outer link 15 has a distance between the two outer link plates 14 facing each other than the inner link 13. A relatively wide link. In the chain 11, the inner links 13 and the outer links 15 are alternately arranged, and the end portions adjacent to each other in the series direction X are sequentially connected to each other in a freely rotatable manner. Is formed.

  It should be noted that the inner link plate 12 of each inner link 13 and the outer link plate 14 of each outer link 15 in the chain 11 of this embodiment are both moving directions when the chain 11 is pulled and moved from one side in the longitudinal direction. A rounded plate shape extending along the series direction X is formed. The inner link plates 12 and the outer link plates 14 are arranged so as to be parallel to each other.

  Accordingly, in this respect, the chain 11 of the present embodiment is configured such that the distance between the inner link plates 12 and the distance between the outer link plates on the one end side and the other end side of each inner link 13 and each outer link 15 in the series direction X. It can be said that these are so-called flat type chains configured to be equal to each other.

  At both ends of the inner link plate 12, circular bush insertion holes 16 are formed so as to penetrate in the width direction Y, which is also the thickness direction of the inner link plate 12. A cylindrical bush 17 as an example of a bearing is assembled between the two inner link plates 12 facing each other in the inner link 13 so as to maintain the distance between the inner link plates 12.

  Each bush 17 is fitted into the bush insertion hole 16 of each inner link plate 12 at both ends so as to bridge between the two inner link plates 12 facing each other. Each bush 17 is inserted through a cylindrical roller 18 and rotatably supports each roller 18. That is, each bush 17 is loosely fitted to each roller 18.

  At both ends of the outer link plate 14, circular pin insertion holes 20 into which cylindrical pins 19 as examples of shafts each having an outer diameter slightly smaller than the inner diameter of the bush 17 can be fitted. It is formed so as to penetrate in the width direction Y which is also the thickness direction. The outer link plate 14 of the outer link 15 is connected to the inner link 13 from the outside of the inner link plate 12 in the inner link 13 formed by assembling the bush 17 between the two inner link plates 12 via the cylindrical pins 19. 13 inner link plates 12 are rotatably connected.

  In this case, the pin 19 is inserted into the bush 17 assembled between the two inner link plates 12 of the inner link 13 at the intermediate portion other than both ends, and both ends of the outer link plate 14 of the outer link 15 at the both ends. It is inserted into the pin insertion hole 20. Therefore, when the two inner link plates 12 of the inner links 13 adjacent to each other in the series direction X and the two outer link plates 14 of the outer links 15 are rotatably connected to each other by the pins 19 and the bushes 17. I can say that. The chain 11 is made of, for example, metal.

  As shown in FIGS. 2 and 3, the cylindrical bush 17 is formed by compressing a metal powder KF (see FIG. 12C), which will be described later, into a predetermined shape and molding 50 (FIG. 12J). Reference) is sintered. For this reason, the bush 17 is a porous bearing and has many pores. The inner peripheral surface of the bush 17 is a bearing surface 30 that slidably receives and supports the pin 19. A plurality of elongated recesses 31 extending in the width direction Y are arranged at equal intervals in the circumferential direction of the bushing 17 (eight in the present embodiment) at the central portion of the bearing surface 30 in the width direction Y which is also the axial direction of the bushing 17. ) Is formed.

Next, the configuration of a mold apparatus for molding the bush 17 will be described.
As shown in FIG. 4, the mold apparatus 35 includes a substantially cylindrical lower punch 36 arranged in a fixed state, a cylindrical die 37 slidably fitted to the lower punch 36, and a lower punch 36. And a core rod 38 that is slidably inserted in the upper punch 39 and a substantially cylindrical upper punch 39 that is disposed immediately above the lower punch 36 and is slidably inserted into the die 37. The die 37, the core rod 38, and the upper punch 39 can be moved up and down by a driving force of a driving source (not shown).

  As shown in FIGS. 5 and 6, the core rod 38 includes a hollow case 41 having a covered cylindrical shape. A plurality of elongated through holes 42 extending along the axial direction Z of the case 41 (core rod 38) are arranged on the outer peripheral surface 41a at the tip end portion (the upper end portion in FIG. 5) of the case 41 so as to be equally spaced in the circumferential direction ( In the present embodiment, eight) are formed. In each through hole 42, a projecting / retracting member 43 having a substantially rectangular plate shape for forming the recess 31 (see FIG. 3) of the bush 17 is inserted into and retracted from the outer peripheral surface 41 a side of the case 41. .

  The surface on the outer peripheral surface 41a side of the case 41 in each projecting member 43 is a front end surface, and the both ends of the front end surface in the axial direction Z protrude outwardly in the axial direction Z (centering on the axis of the case 41). The inclined surface 43a is formed so that the height thereof is gradually reduced. On the other hand, the end of each protruding member 43 on the inner peripheral surface 41b side of the case 41 is a base end portion, and the protruding amount of the protruding member 43 from the outer peripheral surface 41a of the case 41 to the outside is constant. A restricting portion 44 for restricting the amount is provided. The restricting portion 44 has a substantially rectangular parallelepiped shape that is slightly larger than the through hole 42, and is located inside the case 41.

  As shown in FIGS. 5 to 7, an engagement pin 45 is inserted along the axial direction Z at the center of the case 41. The engagement pin 45 has a circular shape in a cross-sectional view, and is tapered so that the outer diameter decreases toward the tip. In the case 41, the engaging pins 45 are all surrounded by (eight) protruding and retracting members 43.

  That is, the peripheral surface 45 a of the engagement pin 45 faces the restricting portions 44 of all the protruding and retracting members 43. In this case, as shown in FIG. 11, the facing surface 44 a that faces the peripheral surface 45 a of the engaging pin 45 in the restricting portion 44 of each projecting member 43 corresponds to the peripheral surface 45 a of the engaging pin 45 with the taper. It has an inclined concave curved surface.

  Then, when the engaging pin 45 is pushed to the pushing position pushed in the insertion direction with respect to the case 41 as shown by the solid line in FIG. 11, the peripheral surface 45a of the engaging pin 45 is shown in FIG. It engages with the facing surface 44 a of the restricting portion 44 of the member 43. Then, by this engagement, each projecting member 43 is pressed by the engagement pin 45, and the leading end portion (the end portion on the outer peripheral surface 41a side of the case 41) of each projecting member 43 is shown in FIG. 5 and FIG. Projecting outward from the outer peripheral surface 41 a of the case 41 from the through hole 42. In other words, the engaging pin 45 engages with each of the protruding and retracting members 43, thereby causing a part of each of the protruding and protruding members 43 to protrude from the through holes 42 to the outside of the case 41.

  On the other hand, when the engagement pin 45 is pulled back from the push-in position to the pull-back position which is pulled back in the direction opposite to the insertion direction with respect to the case 41 as shown by a one-dot chain line in FIG. A gap is created between the protruding portion 43 and the opposing surface 44a of the restricting portion 44.

  In this state, when a force pressing toward the through hole 42 is applied to each protruding and retracting member 43, as shown in FIG. 10, each protruding and protruding member 43 is connected to the peripheral surface 45 a of the engaging pin 45 and each protruding and protruding member. It moves so that the clearance gap produced between the opposing surfaces 44a of 43 control parts 44 may be eliminated. Then, as shown in FIGS. 8 and 9, the facing surface 44 a of the restricting portion 44 comes into contact with the peripheral surface 45 a of the engaging pin 45, and the retracting members 43 are retracted into the through holes 42.

Next, a method for manufacturing the bush 17 will be described.
The bush 17 compresses the metal powder into a predetermined cylindrical shape to form a green compact 50 (see FIG. 12 (j)), and sinters the green compact 50 formed in the molding process. It is manufactured by performing a sintering process.

Therefore, the molding process will be described with reference to FIGS. 12 (a) to 12 (j).
When molding the green compact 50, first, as shown in FIG. 12A, the mold apparatus 35 is brought into a standard state. That is, the upper surface of the core rod 38 and the upper surface of the die 37 are aligned with the upper surface of the lower punch 36. Subsequently, as shown in FIG. 12B, the core rod 38 and the die 37 are raised to a predetermined height, and the space S surrounded by the upper surface of the lower punch 36, the peripheral surface of the core rod 38, and the inner peripheral surface of the die 37. Form. At this time, the height of the upper surface of the core rod 38 and the height of the upper surface of the die 37 are the same.

  Subsequently, as shown in FIG. 12C, the powder box 51 containing the metal powder KF containing the metal powder KF and opened on the lower side is slid along the upper surface of the core rod 38 and the upper surface of the die 37, S is filled with metal powder KF. As a result, the upper end portion of the core rod 38 is disposed in the metal powder KF. In this case, as the metal powder KF, for example, iron-based powder, copper-based powder, or a mixed powder obtained by mixing these powders is used.

  Subsequently, the engaging pin 45 of the core rod 38 is pushed to the pushing position, and the engaging pin 45 is engaged with each projecting member 43. Thus, the core rod 38 is in a state in which each projecting member 43 is pressed by the engagement pin 45, and the distal end portion of each projecting member 43 protrudes from each through hole 42 to the outside. Subsequently, as shown in FIG. 12 (d), the powder box 51 is slid along the upper surface of the core rod 38 and the upper surface of the die 37, so that the metal powder KF filled in the space S is worn.

  Subsequently, as shown in FIG. 12E, the die 37 is raised so that the height of the upper surface of the die 37 is higher than the height of the upper surface of the metal powder KF. Subsequently, as shown in FIG. 12F, the upper punch 39 is lowered, and the lower surface of the upper punch 39 is brought into contact with the upper surface of the metal powder KF. At this time, the lower end portion of the upper punch 39 is inserted into the die 37 and the upper end portion of the core rod 38 is inserted into the upper punch 39. Further, at this time, the die 37 descends about half of the descending distance of the upper punch 39.

  Subsequently, as shown in FIG. 12G, the upper punch 39 is lowered to pressurize and compress the metal powder KF. Thereby, the metal powder KF becomes the green compact 50. At this time, since the tip end portion of each projecting member 43 protrudes into the metal powder KF from each through hole 42 on the peripheral surface of the core rod 38, the green compact 50 becomes the bearing surface 30 and the recess 31 of the bush 17. Parts are formed simultaneously. Subsequently, the upper punch 39 is slightly raised to release the pressed state of the green compact 50. At this time, the die 37 is also raised slightly.

  Subsequently, as shown in FIG. 12 (h), the die 37 is lowered until the upper surface thereof is flush with the upper surface of the lower punch 36. Subsequently, as shown in FIG. 12I, the upper punch 39 is raised. Subsequently, as shown in FIG. 12 (j), the core rod 38 is lowered until the upper surface thereof is flush with the upper surface of the lower punch 36.

  That is, the core rod 38 is pulled out from the green compact 50 along the vertical direction that is the axial direction Z thereof. At this time, the core rod 38 is pulled out from the green compact 50 after the engagement pin 45 is pulled back from the pushed-in position to the pull-back position and the engagement state between each projecting member 43 and the engagement pin 45 is released. This completes the molding process.

Here, the action when the core rod 38 is pulled out from the green compact 50 will be described with reference to FIGS. 13 (a) to 13 (c).
As shown in FIG. 13A, in the state where the green compact 50 is molded, the inclined surface 50 a corresponding to the inclined surface 43 a of the projecting member 43 is formed in the concave portion 31 of the green compact 50. When the core rod 38 is moved downward from the green compact 50, the inclined surface 43 a of the projecting member 43 slides on the slope 50 a of the green compact 50. In this case, since the direction H in which the core rod 38 is pulled out from the green compact 50 coincides with the lower side, the lower inclined surface 43a of the projecting member 43 has a lower height in the protruding direction.

  Then, the intruding member 43 is gradually pushed into the through hole 42 as shown in FIG. 13B by receiving a pressing force (reaction force) from the inclined surface 50a of the green compact 50 on the inclined surface 43a. . Subsequently, when the core rod 38 is moved so as to be pulled out downward, and the inclined surface 43a of the intruding member 43 moves below the inclined surface 50a of the green compact 50, the intruding member 43 is shown in FIG. In such a manner, it is completely pushed into the through hole 42. As a result, the resistance by the retracting member 43 when the core rod 38 is pulled out from the green compact 50 is reduced, so that the core rod 38 is smoothly pulled out from the green compact 50.

  As described above, the green compact 50 molded in the molding process is subjected to a sintering process in which it is sintered and sintered in a sintering furnace (not shown), and then sizing or surface treatment as necessary. Is performed, and the bush 17 is obtained. In the bush 17 manufactured in this way, since the recess 31 is formed in the molding process, the pores of the bearing surface 30 where the recess 31 is formed are prevented from being crushed during manufacturing.

  For this reason, the portion of the bearing surface 30 of the bush 17 where the recess 31 is formed and the portion where the recess 31 is not formed are in the same state where they are not crushed. Therefore, when lubricating oil is included in the bush 17, the lubricating oil can be uniformly and stably exuded from the pores of the bearing surface 30.

According to the embodiment detailed above, the following effects are exhibited.
(1) As for the porous bush 17, the recessed part 31 is formed in a formation process. For this reason, it can suppress that the pore of the part in which the recessed part 31 in the bush 17 was formed is crushed at the time of manufacture of the bush 17. FIG.

  (2) In the bush 17, the bearing surface 30 and the recess 31 are formed by compressing the metal powder KF in a state where the core rod 38 is disposed in the metal powder KF in the molding process. For this reason, the bearing surface 30 and the recessed part 31 in the bush 17 can be formed at once. Therefore, it is not necessary to perform a step of forming the recess 31 in the bearing surface 30 of the bush 17 after the sintering step.

  (3) The retracting member 43 is protruded from the through hole 42 by engaging with the engaging pin 45 in the forming process, and the core rod 38 is formed between the retracting member 43 and the engaging pin 45 after the green compact 50 is formed. After the engaged state is released, the core rod 38 is pulled out from the green compact 50 along the axial direction Z. For this reason, by releasing the engagement state of the protrusion / disengagement member 43 and the engagement pin 45, the protrusion / distraction member 43 is allowed to enter the through hole 42, so that the core rod 38 can be pulled out of the green compact 50. it can.

  (4) The projecting and retracting member 43 has an inclined surface 43a at the end on the direction H side in which the core rod 38 is pulled out from the green compact 50 so that the height in the protruding direction decreases in the direction H in the pulling out direction. For this reason, when the core rod 38 is pulled out from the green compact 50, the projecting and retracting member 43 receives a pressing force (reaction force) from the inclined surface 50a of the green compact 50 corresponding to the inclined surface 43a on the inclined surface 43a. The retracting member 43 is pressed into the through hole 42. For this reason, since the resistance by the protruding and retracting member 43 when the core rod 38 is pulled out from the green compact 50 is reduced, the core rod 38 can be easily pulled out from the green compact 50.

  (5) In the porous bush 17, the pores of the bearing surface 30 where the recesses 31 are formed and the pores where the recesses 31 are not formed are in the same state. For this reason, when the lubricating oil is included in the bush 17, the lubricating oil can be oozed out from the pores of the bearing surface 30 evenly and stably. Furthermore, since excess lubricating oil can be absorbed from the pores of the bearing surface 30 and returned into the bushing 17, it is possible to suppress the lubricating oil from leaking out and being exhausted. In addition, since the lubricating oil can be circulated inside and outside the bush 17, deterioration of the bush 17 and the pin 19 can be suppressed.

(Example of change)
In addition, you may change the said embodiment as follows.
-At least one may be abbreviate | omitted among the two inclined surfaces 43a in the intruding member 43. FIG.

  The core rod 38 may include an actuator that moves between the position where the protruding and retracting member 43 protrudes from the through hole 42 and the position where the core member 38 is accommodated in the through hole 42 instead of the engagement pin 45.

The bearing surface 30 and the recess 31 of the bush 17 do not necessarily have to be formed using the core rod 38 in the molding process.
In FIG. 12 (g), after pressing the metal powder KF and compressing the green compact 50, the upper punch 39 is lifted slightly to release the pressed state of the green compact 50, The core rod 38 may be pulled out from the green compact 50.

  The operation of projecting each protruding member 43 of the core rod 38 from each through hole 42 to the outside may be performed when the space S is formed as shown in FIG. 12B, or FIG. As shown in FIG. 6, the metal powder KF filled in the space S may be cut off.

-You may change suitably the number and shape of the recessed part 31 of the bush 17. FIG.
The bearing may be a hydrodynamic bearing that generates pressure when a fluid such as lubricating oil flows by rotation of a shaft to be received. The hydrodynamic bearing is employed for a hard disk or a fan, for example.

A bearing other than the bush 17 may be used, and for example, a bearing that receives a rotating shaft of a motor may be used.
-A bearing may not be a cylindrical thing but a semi-cylindrical thing, for example.

  DESCRIPTION OF SYMBOLS 17 ... Bush as an example of a bearing, 19 ... Pin as an example of a shaft, 30 ... Bearing surface, 31 ... Recessed part, 38 ... Core rod, 41 ... Case, 42 ... Through-hole, 43 ... Projection member, 43a ... Inclined surface, 45 ... engaging pin, 50 ... green compact, KF ... metal powder, H ... direction of drawing.

Claims (6)

A method of manufacturing a porous bearing constituted by a sintered body and having a recess on a bearing surface that receives a shaft,
A molding process in which a metal powder is compressed to form a green compact;
A sintering step of sintering the green compact molded in the molding step,
The method of manufacturing a bearing, wherein the recess is formed in the molding step.   The bearing manufacturing method according to claim 1, wherein the bearing surface and the recess are formed by compressing the metal powder in a state where a core rod is disposed in the metal powder in the forming step. The core rod is
A hollow case having a through-hole in the peripheral surface;
A retractable member inserted in the through hole so as to be freely retractable;
An engagement pin that is inserted into the case and engages with the in / out member to project the in / out member from the through hole,
The intruding member is protruded from the through hole by engagement with the engagement pin in the molding step,
The core rod is pulled out from the green compact along the axial direction of the core rod after the green compact is formed and the engagement state of the projecting member and the engagement pin is released. The bearing manufacturing method according to claim 2.   4. The protruding and retracting member has an inclined surface whose height in the projecting direction decreases in the direction of pulling out at an end portion in the direction of pulling out the core rod from the green compact. The manufacturing method of the bearing as described in 2 .. A porous bearing composed of a sintered body and having a recess on the bearing surface that receives the shaft,
It is manufactured by performing at least a forming step of compressing metal powder to form a green compact and a sintering step of sintering the green compact formed in the forming step,
The said recessed part is formed in the said formation process, The bearing characterized by the above-mentioned. A porous bearing composed of a sintered body and having a recess on the bearing surface that receives the shaft,
By forming the concave portion in a molding step of compressing metal powder to form a green compact, the pores in the bearing surface where the concave portions are formed and the pores where the concave portions are not formed Bearings characterized by being in the same state.